Modulating immunity as a therapy for bacterial infections

Vitamin D receptor activated by vitamin D administration alleviates Mycobacterium tuberculosis-induced bone destruction by inhibiting NFκB-mediated aberrant osteoclastogenesis

Clinically, bone destruction caused by Mycobacterium tuberculosis was serious especially in patients with vitamin D (VD) deficiency. However, the role of VD in M. tuberculosis-induced bone destruction remains clear. In this context, we investigate the role of VD and vitamin D receptor (VDR) in the M. tuberculosis-induced bone destruction. First, we infected RAW264.7 and bone marrow-derived macrophages (BMMs) with Mycobacterium bovis Bacillus Calmette-Guérin (M. bovis BCG) in vitro. Then, we activated VDR through VD administration. TRAP and FAK staining, bone resorption assays, immunofluorescence staining, qPCR, and western blot were carried out. In vivo, the M. tuberculosis-induced osteolytic model on the murine skull was established and the μCT and histological analyses were performed. We found that VDR and TRAP were upregulated in bone tuberculosis tissue and proved that M. tuberculosis infection promoted osteoclastogenesis in RAW264.7 and BMMs. VD could inhibit osteoclasts differentiation, fusion, and bone resorption dose-dependently. However, when VDR was knocked down, the inhibitory effect of VD on osteoclasts disappeared. In mechanism, activation of VDR inhibits the phosphorylation of IκB α, thereby inhibiting NFκB signaling pathway and alleviating osteoclastogenesis. Furthermore, in the skull osteolysis model, VD administration reduced osteolysis, but not in VDR^-/- mice. Our study, for the first time, demonstrates that activation of VDR by VD administration inhibits M. tuberculosis-induced bone destruction. Our results reveal that VD and VDR are potential therapeutic targets for M. tuberculosis-induced bone destruction, and are of great clinical significance for the development of new therapeutic strategies.

Tetrasubstituted imidazoles as incognito Toll-like receptor 8 a(nta)gonists

Small-molecule modulators of TLR8 have drawn much interests as it plays pivotal roles in the innate immune response to single-stranded RNAs (ssRNAs) derived from viruses. However, their clinical uses are limited because they can invoke an uncontrolled, global inflammatory response. The efforts described herein culminate in the fortuitous discovery of a tetrasubstituted imidazole CU-CPD107 which inhibits R848-induced TLR8 signaling. In stark contrast, CU-CPD107 shows unexpected synergistic agonist activities in the presence of ssRNA, while CU-CPD107 alone is unable to influence TLR8 signaling. CU-CPD107’s unique, dichotomous behavior sheds light on a way to approach TLR agonists. CU-CPD107 offers the opportunity to avoid the undesired, global inflammation side effects that have rendered imidazoquinolines clinically irrelevant, providing an insight for the development of antiviral drugs.

Toll-like receptor 8 (TLR8) plays essential roles in the innate immune response to viral single-stranded RNA (ssRNA), so small molecule modulators of TLR8 are of interest, however adverse effects limit their use. Here, the authors report a tetrasubstituted imidazole CU-CPD107 with dichotomous behaviour, which inhibits R848-induced TLR8 signaling, but shows synergistic activity in the presence of ssRNA, making it a potential antiviral agent.

Cathelicidin and PMB neutralize endotoxins by multifactorial mechanisms including LPS interaction and targeting of host cell membranes

Antimicrobial peptides (AMPs) contribute to an effective protection against infections. The antibacterial function of AMPs depends on their interactions with microbial membranes and lipids, such as lipopolysaccharide (LPS; endotoxin). Hyperinflammation induced by endotoxin is a key factor in bacterial sepsis and many other human diseases. Here, we provide a comprehensive profile of peptide-mediated LPS neutralization by systematic analysis of the effects of a set of AMPs and the peptide antibiotic polymyxin B (PMB) on the physicochemistry of endotoxin, macrophage activation, and lethality in mice. Mechanistic studies revealed that the host defense peptide LL-32 and PMB each reduce LPS-mediated activation also via a direct interaction of the peptides with the host cell. As a biophysical basis, we demonstrate modifications of the structure of cholesterol-rich membrane domains and the association of glycosylphosphatidylinositol (GPI)-anchored proteins. Our discovery of a host cell-directed mechanism of immune control contributes an important aspect in the development and therapeutic use of AMPs.

Sublancin protects against methicillin-resistant Staphylococcus aureus infection by the combined modulation of innate immune response and microbiota

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for community and hospital bacterial infections. In the present study, the protective role of sublancin, an antimicrobial peptides, was explored in MRSA infection model. We report that sublancin directly induce macrophage migration through the chemotactic receptors. We further show that sublancin exhibits protection in a mouse MRSA infection model. This protection involved an immunomodulatory activity, but was blocked by depletion of monocyte/macrophages or neutrophils. Sublancin selectively up-regulates the levels of chemokines (C-X-C motif chemokine ligand 1, CXCL1 and monocyte chemoattractant protein-1, MCP-1) while reducing the production of pro-inflammatory cytokine (tumor necrosis factor-α, TNF-α). Meanwhile, sublancin regulated the microbiota composition disrupted by MRSA injection, increasing the abundance of Lactobacillus and decreasing that of Staphylococcus and Pseudomonas. Also, sublancin restored to normal levels of metabolic functional pathways, especially amino acid biosynthesis (e.g., branched amino acid, histidine and tryptophan), disrupted after injection, and this restoration was significantly correlated with neutrophils. These results demonstrates that sublancin stimulates the innate response and modulates the microbiota community to protect against MRSA infection.

Controlling Peptide Function by Directed Assembly Formation: Mechanistic Insights Using Multiscale Modeling on an Antimicrobial Peptide-Drug-Membrane System

Owing to their potential applicability against multidrug-resistant bacteria, antimicrobial peptides (AMPs) or host defense peptides (HDPs) gain increased attention. Besides diverse immunomodulatory roles, their classical mechanism of action mostly involves membrane disruption of microbes. Notably, their unbalanced overexpression has also been associated with host cell cytotoxicity in various diseases. Relatedly, AMPs can be subject to aggregate formation, either via self-assembly or together with other compounds, which has demonstrated a modulation effect on their biological functions, thus highly relevant both for drug targeting projects and understanding their in vivo actions. However, the molecular aspects of the related assembly formation are not understood. Here, we focused in detail on an experimentally studied AMP-drug system, i.e., CM15-suramin, and performed all-atom and coarse-grain (CG) simulations. Results obtained for all systems were in close line with experimental observations and indicate that the CM15-suramin aggregation is an energetically favorable and dynamic process. In the presence of bilayers, the peptide-drug assembly formation was highly dependent on lipid composition, and peptide aggregates themselves were also capable of binding to the membranes. Interestingly, longer CG simulations with zwitterionic membranes indicated an intermediate state in the presence of both AMP-drug assemblies and monomeric peptides located on the membrane surface. In sharp contrast, larger AMP-drug aggregates could not be detected with a negatively charged membrane, rather the AMPs penetrated its surface in a monomeric form, in line with previous in vitro observations. Considering experimental and theoretical results, it is promoted that in biological systems, cationic AMPs may often form associates with anionic compounds in a reversible manner, resulting in lower bioactivity. This is only mildly affected by zwitterionic membranes; however, membranes with a negative charge strongly alter the energetic preference of AMP assemblies, resulting in the dissolution of the complexes into the membrane. The phenomenon observed here at a molecular level can be followed in several experimental systems studied recently, where peptides interact with food colors, drug molecules, or endogenous compounds, which strongly indicates that reversible associate formation is a general phenomenon for these complexes. These results are hoped to be exploited in novel therapeutic strategies aiming to use peptides as drug targets and control AMP bioactivity by directed assembly formation.

Macrophages as a "weapon" in anticancer cellular immunotherapy

Anticancer immunotherapy is a treatment that activates the immune system to fight the tumor. Immunotherapy has several advantages over other cancer treatments in that anticancer immunotherapy displays high specificity, low side effects, and can combine with various conventional therapies. In recent years, oncologists have shown increasing interest in using macrophages for adoptive cell therapy and predict a bright future of macrophage-directed therapy for eliminating cancer. The focus of increased research interest is the classically activated M1 macrophages exhibiting pronounced tumoricidal activity, and the alternatively activated M2 tumor-associated macrophages, which otherwise help malignant cells evading attack by the immune system. M1 macrophages may represent an effective weapon in anticancer cellular immunotherapy, and the use of autoimmune macrophages properly prepared for antitumor administration is one of the promising ways for personalized therapy of cancer patients. The present report mainly discusses some modern aspects of the problem in application of activated M1 macrophage in anticancer therapy and reviews relevant publications up to 2021.

Basil Polysaccharide Reverses Development of Experimental Model of Sepsis-Induced Secondary Staphylococcus aureus Pneumonia

Background

Basil polysaccharide (BPS) represents a main active ingredient extracted from basil (Ocimum basilicum L.), which can regulate secondary bacterial pneumonia development in the process of sepsis-mediated immunosuppression.

Methods

In this study, a dual model of sepsis-induced secondary pneumonia with cecal ligation and puncture and intratracheal instillation of Staphylococcus aureus or Pseudomonas aeruginosa was constructed.

Results

The results indicated that BPS-treated mice undergoing CLP showed resistance to secondary S. aureus pneumonia. Compared with the IgG-treated group, BPS-treated mice exhibited better survival rate along with a higher bacterial clearance rate. Additionally, BPS treatment attenuated cell apoptosis, enhanced lymphocyte and macrophage recruitment to the lung, promoted pulmonary cytokine production, and significantly enhanced CC receptor ligand 4 (CCL4). Notably, recombinant CCL4 protein could enhance the protective effect on S. aureus-induced secondary pulmonary infection of septic mice, which indicated that BPS-induced CCL4 partially mediated resistance to secondary bacterial pneumonia. In addition, BPS priming markedly promoted the phagocytosis of alveolar macrophages while killing S. aureus in vitro, which was related to the enhanced p38MAPK signal transduction pathway activation. Moreover, BPS also played a protective role in sepsis-induced secondary S. aureus pneumonia by inducing Treg cell differentiation.

Conclusions

Collectively, these results shed novel lights on the BPS treatment mechanism in sepsis-induced secondary S. aureus pneumonia in mice.

Polyvalent Bacterial Lysate Protects Against Pneumonia Independently of Neutrophils, IL-17A or Caspase-1 Activation

Polyvalent bacterial lysates have been in use for decades for prevention and treatment of respiratory infections with reported clinical benefits. However, besides claims of broad immune activation, the mode of action is still a matter of debate. The lysates, formulated with the main bacterial species involved in respiratory infections, are commonly prepared by chemical or mechanical disruption of bacterial cells, what is believed influences the biological activity of the product. Here, we prepared two polyvalent lysates with the same composition but different method of bacterial cell disruption and evaluated their biological activity in a comparative fashion. We found that both bacterial lysates induce NF-kB activation in a MyD88 dependent manner, suggesting they work as TLR agonists. Further, we found that a single intranasal dose of any of the two lysates, is sufficient to protect against pneumococcal pneumonia, suggesting that they exert similar biological activity. We have previously shown that protection against pneumococcal pneumonia can also be induced by prior S. pneumoniae sub lethal infection or therapeutic treatment with a TLR5 agonist. Protection in those cases depends on neutrophil recruitment to the lungs, and can be associated with increased local expression of IL-17A. Here, we show that bacterial lysates exert protection against pneumococcal pneumonia independently of neutrophils, IL-17A or Caspase-1/11 activation, suggesting the existence of redundant mechanisms of protection. Trypsin-treated lysates afford protection to the same extent, suggesting that just small peptides suffice to exert the protective effect or that the molecules responsible for the protective effect are not proteins. Understanding the mechanism of action of bacterial lysates and deciphering the active components shall allow redesigning them with more precisely defined formulations and expanding their range of action.

The Use of Translational Modelling and Simulation to Develop Immunomodulatory Therapy as an Adjunct to Antibiotic Treatment in the Context of Pneumonia

The treatment of respiratory tract infections is threatened by the emergence of bacterial resistance. Immunomodulatory drugs, which enhance airway innate immune defenses, may improve therapeutic outcome. In this concept paper, we aim to highlight the utility of pharmacometrics and Bayesian inference in the development of immunomodulatory therapeutic agents as an adjunct to antibiotics in the context of pneumonia. For this, two case studies of translational modelling and simulation frameworks are introduced for these types of drugs up to clinical use. First, we evaluate the pharmacokinetic/pharmacodynamic relationship of an experimental combination of amoxicillin and a TLR4 agonist, monophosphoryl lipid A, by developing a pharmacometric model accounting for interaction and potential translation to humans. Capitalizing on this knowledge and associating clinical trial extrapolation and statistical modelling approaches, we then investigate the TLR5 agonist flagellin. The resulting workflow combines expert and prior knowledge on the compound with the in vitro and in vivo data generated during exploratory studies in order to construct high-dimensional models considering the pharmacokinetics and pharmacodynamics of the compound. This workflow can be used to refine preclinical experiments, estimate the best doses for human studies, and create an adaptive knowledge-based design for the next phases of clinical development.

Erythropoietin Promotes Infection Resolution and Lowers Antibiotic Requirements in E. coli- and S. aureus-Initiated Infections

Endogenous mechanisms underlying bacterial infection resolution are essential for the development of novel therapies for the treatment of inflammation caused by infection without unwanted side effects. Herein, we found that erythropoietin (EPO) promoted the resolution and enhanced antibiotic actions in Escherichia coli (E. coli)- and Staphylococcus aureus (S. aureus)-initiated infections. Levels of peritoneal EPO and macrophage erythropoietin receptor (EPOR) were elevated in self-limited E. coli-initiated peritonitis. Myeloid-specific EPOR-deficient mice exhibited an impaired inflammatory resolution and exogenous EPO enhanced this resolution in self-limited infections. Mechanistically, EPO increased macrophage clearance of bacteria via peroxisome proliferator-activated receptor γ (PPARγ)-induced CD36. Moreover, EPO ameliorated inflammation and increased the actions of ciprofloxacin and vancomycin in resolution-delayed E. coli- and S. aureus-initiated infections. Collectively, macrophage EPO signaling is temporally induced during infections. EPO is anti-phlogistic, increases engulfment, promotes infection resolution, and lowers antibiotic requirements.

Assessing biofilm inhibition and immunomodulatory activity of small amounts of synthetic host defense peptides synthesized using SPOT-array technology

Peptides are promising drug candidates because of their diversity, biocompatibility and spectrum of activities. Here, we describe a protocol for high-throughput screening of SPOT-peptide arrays to assess the antibiofilm, antimicrobial and immunomodulatory activities of synthetic peptides. It is a Protocol Extension of our previous Nature Protocols article, which describes the synthesis of SPOT-peptide arrays and assays for screening antimicrobial activity. This latest protocol allows the simultaneous assessment of hundreds of synthetic host defense peptides to define their overall activity profiles and identify candidate sequences that are suitable for further characterization and development as anti-infectives. When coupled with the SPOT-array technology for peptide synthesis, the described procedures are rapid, inexpensive and straightforward for peptide library screening. The protocols can be implemented in most microbiology or immunology research laboratories without the need for specialists. The time to complete each step ranges between 1 and 4 h with overnight pauses, and datasets related to the antibiofilm and immunomodulatory activities of a large set of peptide sequences can be generated in a few days.

Targeting of myeloid-derived suppressor cells by all-trans retinoic acid as host-directed therapy for human tuberculosis

Conventional anti-tuberculosis (TB) therapies comprise lengthy antibiotic treatment regimens, exacerbated by multi-drug resistant and extensively drug resistant mycobacterial strains. We assessed the ability of all-trans retinoic acid (ATRA), as repurposed compound serving as host-directed therapy (HDT), to counteract the suppressive effects of myeloid-derived suppressor cells (MDSCs) obtained from active TB cases (untreated or during week one of treatment) on T-cell responsiveness. We show for the first time that MDSCs suppress non-specific T-cell activation and production of interleukin (IL)-2, IL-4, IL-13 and GM-CSF via contact-dependent mechanisms. ATRA treatment decreases MDSC frequency, but fails to mature MDSCs to non-suppressive, terminally differentiated myeloid cells and does not restore T-cell function or cytokine production in the presence of MDSCs. The impact of ATRA treatment on improved immunity, using the concentration tested here, is likely to be minimal, but further identification and development of MDSC-targeting TB host-directed therapies are warranted.

Microfluidic Single-Cell Phenotyping of the Activity of Peptide-Based Antimicrobials

Antibiotic resistance is a major challenge for modern medicine, and there is a dire need to refresh the antibiotic development pipeline to treat infections that are resistant to currently available drugs. Peptide-based antimicrobials represent a promising source of novel anti-infectives, but their development is severely impeded due to the lack of suitable techniques to accurately quantify their antimicrobial efficacy. A major problem involves the heterogeneity of cellular phenotypes in response to these peptides, even within a clonal population of bacteria. There is thus a need to develop single-cell resolution assays to quantify drug efficacy for these novel therapeutics. We present here a detailed microfluidics-microscopy protocol for testing the efficacy of peptide-based antimicrobials on hundreds to thousands of individual bacteria in well-defined microenvironments. This enables the study of cell-to-cell differences in drug response within a clonal population. It is a highly versatile tool, which can be used to quantify drug efficacy, including the number of individual survivors at defined drug doses; it even enables the potential exploration of the molecular mechanisms of action of the drug, which are often unknown in the early stages of drug development. We present here protocols for working with Escherichia coli, but organisms of different geometric shapes and sizes may also be tested with suitable modifications of the microfluidic device.

A Bacteria-Inspired Morphology Genetic Biomedical Material: Self-Propelled Artificial Microbots for Metastatic Triple Negative Breast Cancer Treatment

Morphology genetic biomedical materials (MGBMs), referring to fabricating materials by learning from the genetic morphologies and strategies of natural species, hold great potential for biomedical applications. Inspired by the cargo-carrying-bacterial therapy (microbots) for cancer treatment, a MGBM (artificial microbots, AMBs) was constructed. Rather than the inherent bacterial properties (cancerous chemotaxis, tumor invasion, cytotoxicity), AMBs also possessed ingenious nitric oxide (NO) generation strategy. Mimicking the bacterial construction, the hyaluronic acid (HA) polysaccharide was induced as a coating capsule of AMBs to achieve long circulation in blood and specific tissue preference (tumor tropism). Covered under the capsule-like polysaccharide was the combinatorial agent, the self-assembly constructed by the amphiphilic dendrons with abundant l-arginine residues peripherally (as endogenous NO donor) and hydrophobic chemotherapeutic drugs at the core stacking on the surface of SWNTs (the photothermal agent) for a robust chemo-photothermal therapy (chemo-PTT) and the elicited immune therapy. Subsequently, the classic inducible nitric oxide synthase (iNOS) pathway aroused by immune response was revolutionarily utilized to oxidize the l-arginine substrates for NO production, the process for which could also be promoted by the high reactive oxygen species level generated by chemo-PTT. The NO generated by AMBs was intended to regulate vasodilation and cause a dramatic invasion (as the microbots) to disperse the therapeutic agents throughout the solid tumor for a much more enhanced curative effect, which we defined as "self-propulsion". The self-propelled AMBs exhibiting impressive primary tumor ablation, as well as the distant metastasis regression to conquer the metastatic triple negative breast cancer, provided pioneering potential therapeutic opportunities, and enlightened broad prospects in biomedical application.

Recent advances in design of antimicrobial peptides and polypeptides toward clinical translation

The recent outbreaks of infectious diseases caused by multidrug-resistant pathogens have sounded a piercing alarm for the need of new effective antimicrobial agents to guard public health. Among different types of candidates, antimicrobial peptides (AMPs) and the synthetic mimics of AMPs (SMAMPs) have attracted significant enthusiasm in the past thirty years, due to their unique membrane-active antimicrobial mechanism and broad-spectrum antimicrobial activity. The extensive research has brought many drug candidates into clinical and pre-clinical development. Despite tremendous progresses have been made, several major challenges inherent to current design strategies have slowed down the clinical translational development of AMPs and SMAMPs. However, these challenges also triggered many efforts to redesign and repurpose AMPs. In this review, we will first give an overview on AMPs and their synthetic mimics, and then discuss the current status of their clinical translation. Finally, the recent advances in redesign and repurposing AMPs and SMAMPs are highlighted.

Use of Therapeutic Pathogen Recognition Receptor Ligands for Osteo-Immunomodulation

Therapeutic pathogen recognition receptor (PRR) ligands are reaching clinical practice following their ability to skew the immune response in a specific direction. We investigated the effects of various therapeutic PRR ligands on bone cell differentiation and inflammation. Following stimulation, alkaline phosphatase (ALP) activity (Day 10), osteocalcin, osteonectin expression (Day 14), and calcium deposition (Day 21) were quantified in bone marrow-derived human mesenchymal stem cells (hMSCs). The osteoclastogenic response was determined by measuring tartrate-resistant acid phosphate (TRAP) activity in human monocytes. TNF-α, IL-6, IL-8, and IL-10 expressions were measured by enzyme-linked immunosorbent assay as an indicator of the ligands’ inflammatory properties. We found that nucleic acid-based ligands Poly(I:C) and CpG ODN C increased early ALP activity in hMSCs by 4-fold without affecting osteoclast formation. These ligands did not enhance expression of the other, late osteogenic markers. MPLA, Curdlan, and Pam3CSK4 did not affect osteogenic differentiation, but inhibited TRAP activity in monocytes, which was associated with increased expression of all measured cytokines. Nucleic acid-based ligands are identified as the most promising osteo-immunomodulators, as they favor early osteogenic differentiation without inducing an exaggerated immune-cell mediated response or interfering in osteoclastogenesis and thus can be potentially harnessed for multifunctional coatings for bone biomaterials.

MOSPD2 is a receptor mediating the LEAP-2 effect on monocytes/macrophages in a teleost, Boleophthalmus pectinirostris

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic peptide that plays an important role in a host's innate immune system. We previously demonstrated that mudskipper ( Boleophthalmus pectinirostris) LEAP-2 (BpLEAP-2) induces chemotaxis and activation of monocytes/ macrophages (MO/MФ). However, the molecular mechanism by which BpLEAP-2 regulates MO/MΦ remains unclear. In this study, we used yeast two-hybrid cDNA library screening to identify mudskipper protein(s) that interacted with BpLEAP-2, and characterized a sequence encoding motile sperm domain-containing protein 2 (BpMOSPD2). The interaction between BpLEAP-2 and BpMOSPD2 was subsequently confirmed by co-immunoprecipitation (Co-IP). Sequence analyses revealed that the predicted BpMOSPD2 contained an N-terminal extracellular portion composed of a CRAL-TRIO domain and a motile sperm domain, a C-terminal transmembrane domain, and a short cytoplasmic tail. Phylogenetic tree analysis indicated that BpMOSPD2 grouped tightly with fish MOSPD2 homologs and was most closely related to that of the Nile tilapia ( Oreochromis niloticus). The recombinant BpMOSPD2 was produced by prokaryotic expression and the corresponding antibody was prepared for protein concentration determination. RNA interference was used to knockdown BpMOSPD2 expression in the mudskipper MO/MФ, and the knockdown efficiency was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. Knockdown of BpMOSPD2 significantly inhibited BpLEAP-2-induced chemotaxis of mudskipper MO/MФ and BpLEAP-2-induced bacterial killing activity. Furthermore, knockdown of BpMOSPD2 inhibited the effect of BpLEAP-2 on mRNA expression levels of BpIL-10, BpTNFα, BpIL-1β, and BpTGFβ in MO/MФ. In general, BpMOSPD2 directly interacted with BpLEAP-2, and mediated the effects of BpLEAP-2 on chemotaxis and activation of mudskipper MO/MФ. This is the first identification of MOSPD2 as a receptor for LEAP-2.

Differential Immunomodulatory Effect of Carbon Dots Influenced by the Type of Surface Passivation Agent

Carbon nanodots (CDs) are often synthesized from natural sources including honey, molasses, fruits, and foods, and plant extracts simply through caramelization. They have wide biological applications especially as drug delivery vehicles and bioimaging agent due to their small size and biocompatibility. This article details the synthesis of carbon dots from carob and its derivatives by surface passivation with polyethylene glycol (PEG), polyvinyl alcohol (PVA), and alginate (ALG). We investigated the immune response against CDs and evaluated the effect of surface passivation agents on their immunomodulatory functions. CD_PVA had strong anti-inflammatory activities, whereas CD_ALG were pro-inflammatory. CD_PEG had mild anti-inflammatory activities suggesting that these CDs can be used in the drug delivery studies as inert carriers. These results showed that depending on the type of activated groups dominated on the surface, CDs exerted differential effects on the inflammatory potential of the macrophages by changing the pro-inflammatory TNFα and IL6 production levels.

Trial Watch: Experimental Toll-like receptor agonists for cancer therapy

Toll-like receptors (TLRs) are prototypic pattern recognition receptors (PRRs) best known for their ability to activate the innate immune system in response to conserved microbial components such as lipopolysaccharide and double-stranded RNA. Accumulating evidence indicates that the function of TLRs is not restricted to the elicitation of innate immune responses against invading pathogens. TLRs have indeed been shown to participate in tissue repair and injury-induced regeneration as well as in adaptive immune responses against cancer. In particular, TLR4 signaling appears to be required for the efficient processing and cross-presentation of cell-associated tumor antigens by dendritic cells, which de facto underlie optimal therapeutic responses to some anticancer drugs. Thus, TLRs constitute prominent therapeutic targets for the activation/intensification of anticancer immune responses. In line with this notion, long-used preparations such as the Coley toxin (a mixture of killed Streptococcus pyogenes and Serratia marcescens bacteria) and the bacillus Calmette-Guérin (BCG, an attenuated strain of Mycobacterium bovis originally developed as a vaccine against tuberculosis), both of which have been associated with consistent anticancer responses, potently activate TLR2 and TLR4 signaling. Today, besides BCG, only one TLR agonist is FDA-approved for therapeutic use in cancer patients: imiquimod. In this Trial Watch, we will briefly present the role of TLRs in innate and cognate immunity and discuss the progress of clinical studies evaluating the safety and efficacy of experimental TLR agonists as immunostimulatory agents for oncological indications.

Profiles of expression pattern and tissue distribution of host defense peptides genes in different chicken (Gallus gallus) breeds related to body weight

Host defense peptides (HDPs) are an important first line of defense with antimicrobial and immunomodulatory properties. Selection for increased body weight is hypothesized to be related to reduced immune response. We studied the relationships among body weight, age, and the HDP expression patterns in intestine and immune organs. We used chickens with marked differences of body sizes. The non-selected Daweishan mini chickens showed the highest indexes of immune organs and the lowest concentrations of the plasma immune parameters C3, C4, IgA, and IgY, while the commercial Avian broiler showed the opposite results. The Daweishan mini chickens showed the highest mRNA expressions of HDP genes in small intestine followed by the semi-selected Wuding chickens. Compared with local breeds, broiler chickens showed higher mRNA expression of HDP genes in spleen, thymus, and bursa. Body weight and HDP expression levels were negatively correlated in the intestine and positively in the immune organs. Our results indicated that the HDP immune regulatory roles in small intestine acted as first line of defense in innate immunity in local breeds, and as an adaptive immunity in broiler chickens. Selection was associated with different expression expressions of HDP genes in breed-, age-, and organ-specific manners.

Avian host defense cathelicidins: structure, expression, biological functions, and potential therapeutic applications

Host defense peptides (HDP) are multifunctional effectors of the innate immune system, which has antimicrobial and pleiotropic immunomodulatory functions. Although there is a very sophisticated superposition of adaptive immune systems in vertebrates, this system is still essential. As an important family of HDP, cathelicidins are also known for their broad-spectrum antibacterial activity against bacteria, fungi, and enveloped viruses. It has been found in humans and other species, including cattle, pigs, sheep, goats, chickens, rabbits, and some kind of fish. Among them, cathelicidins in birds were described for the first time in 2005. This review focuses on the structure, biological activities, expression, and regulation of avian cathelicidin, especially main effects of host defense cathelicidin on potential therapeutic applications. According to the results obtained both in vitro and in vivo, good perspectives have been opened for cathelicidin. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of cathelicidin as novel therapeutic alternatives to antibiotics.

Host Defense Peptide-Mimicking Amphiphilic β-Peptide Polymer (Bu:DM) Exhibiting Anti-Biofilm, Immunomodulatory, and in Vivo Anti-Infective Activity

Therapeutic options to treat multidrug resistant bacteria, especially when present in biofilms, are limited due to their high levels of antibiotic resistance. Here, we report the anti-biofilm and immunomodulatory activities of the host defense peptide (HDP)-mimicking β-peptide polymer (20:80 Bu:DM) and investigated its activity in vivo. The polymer outperformed antibiotics in the removal and reduction of the viability of established biofilms, achieving a maximum activity of around 80% reduction in viability. Interestingly the polymer also exhibited HDP-like immunomodulation in inducing chemokines and anti-inflammatory cytokines and suppressing lipopolysaccharide-induced proinflammatory cytokines. When tested in a murine, high-density skin infection model using P. aeruginosa LESB58, the polymer was effective in diminishing abscess size and reducing bacterial load. This study demonstrates the dual functionality of HDP-mimicking β-peptide polymers in inhibiting biofilms and modulating innate immunity, as well as reducing tissue dermonecrosis.

Effect of Secondary Structure and Side Chain Length of Hydrophobic Amino Acid Residues on the Antimicrobial Activity and Toxicity of 14-Residue-Long de novo AMPs

Herein we report the efficacy and toxicity of three de novo designed cationic antimicrobial peptides (AMPs) LL-14, VV-14 and ββ-14, where side chains of the hydrophobic amino acids were reduced gradually. The AMPs showed broad-spectrum antimicrobial activity against three pathogens from the ESKAPE group and two fungal strains. This study showed that side chains which are either too long or too short increase toxicity and lower antimicrobial activity, respectively. VV-14 was found to be non-cytotoxic and highly potent under physiological salt concentrations against several pathogens, especially Salmonella typhi TY2. These AMPs acted via membrane deformation, depolarization, and lysis. The activity of the AMPs is related to their ability to take on amphipathic helical conformations in the presence of microbial membrane mimics. Among AMPs with the same charge, hydrophobic interactions between the side chains of the residues with cell membrane lipids determine their antimicrobial potency and cytotoxicity. Strikingly, an optimum hydrophobic interaction is the crux of generating highly potent non-cytotoxic AMPs.

Strategies for antimicrobial peptide coatings on medical devices: a review and regulatory science perspective

Indwelling and implanted medical devices are subject to contamination by microbial pathogens during surgery, insertion or injection, and ongoing use, often resulting in severe nosocomial infections. Antimicrobial peptides (AMPs) offer a promising alternative to conventional antibiotics to reduce the incidence of such infections, as they exhibit broad-spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria, microbial biofilms, fungi, and viruses. In this review-perspective, we first provide an overview of the progress made in this field over the past decade with an emphasis on the local release of AMPs from implant surfaces and immobilization strategies for incorporating these agents into a wide range of medical device materials. We then provide a regulatory science perspective addressing the characterization and testing of AMP coatings based on the type of immobilization strategy used with a focus on the US market regulatory niche. Our goal is to help narrow the gulf between academic studies and preclinical testing, as well as to support a future literature base in order to develop the regulatory science of antimicrobial coatings.

A highly efficient hybrid peptide ameliorates intestinal inflammation and mucosal barrier damage by neutralizing lipopolysaccharides and antagonizing the lipopolysaccharide-receptor interaction

Intestinal inflammatory disorders, such as inflammatory bowel disease, are major contributors to mortality and morbidity in humans and animals worldwide. While some native peptides have great potential as therapeutic agents against intestinal inflammation, potential cytotoxicity, anti-inciting action, and suppression of anti-inflammatory activity may limit their development as anti-inflammatory agents. Peptide hybridization is an effective approach for the design and engineering of novel functional peptides because hybrid peptides combine the advantages and benefits of various native peptides. In the present study, a novel hybrid anti-inflammatory peptide that combines the active center of Cecropin A (C) and the core functional region of LL-37 (L) was designed [C-L peptide; C (1-8)-L (17-30)] through in silico analysis to reduce cytotoxicity and improve the anti-inflammatory activity of the parental peptides. The resulting C-L peptide exhibited lower cytotoxicity than either C or L peptides alone. C-L also exerted a protective effect against lipopolysaccharide (LPS)-induced inflammatory responses in RAW264.7 macrophages and in the intestines of a mouse model. The hybrid peptide exhibited increased anti-inflammatory activity compared to the parental peptides. C-L plays a role in protecting intestinal tissue from damage, LPS-induced weight loss, and leukocyte infiltration. In addition, C-L reduces the expression levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-1β, and interferon-gamma (IFN-γ), as well as reduces cell apoptosis. It also reduced mucosal barrier damage caused by LPS. The anti-inflammatory effects of the hybrid peptide were mainly attributed to its LPS-neutralizing activity and antagonizing the activation of LPS-induced Toll-like receptor 4-myeloid differentiation factor 2 (TLR4/MD2). The peptide also affected the TLR4-(nuclear factor κB) signaling pathway, modulating the inflammatory response upon LPS stimulation. Collectively, these findings suggest that the newly designed peptide, C-L, could be developed into a novel anti-inflammatory agent for animals or humans.

Combating Implant Infections: Shifting Focus from Bacteria to Host

The widespread use of biomaterials to support or replace body parts is increasingly threatened by the risk of implant-associated infections. In the quest for finding novel anti-infective biomaterials, there generally has been a one-sided focus on biomaterials with direct antibacterial properties, which leads to excessive use of antibacterial agents, compromised host responses, and unpredictable effectiveness in vivo. This review sheds light on how host immunomodulation, rather than only targeting bacteria, can endow biomaterials with improved anti-infective properties. How antibacterial surface treatments are at risk to be undermined by biomaterial features that dysregulate the protection normally provided by critical immune cell subsets, namely, neutrophils and macrophages, is discussed. Accordingly, how the precise modification of biomaterial surface biophysical cues, or the incorporation of immunomodulatory drug delivery systems, can render biomaterials with the necessary immune-compatible and immune-protective properties to potentiate the host defense mechanisms is reviewed. Within this context, the protective role of host defense peptides, metallic particles, quorum sensing inhibitors, and therapeutic adjuvants is discussed. The highlighted immunomodulatory strategies may lay a foundation to develop anti-infective biomaterials, while mitigating the increasing threat of antibacterial drug resistance.

Alantolactone Enhances the Phagocytic Properties of Human Macrophages and Modulates Their Proinflammatory Functions

Aim of the Study

Phagocytosis is a crucial element of innate immune defense involved in bacterial killing. The aim of our study was to evaluate the influence of alantolactone on phagocytosis and cytokines release by THP1-derived macrophages. We assessed whether antimicrobial compound alantolactone (a sesquiterpene lactone present in Inula helenium L.) is able to stimulate immune functions of macrophages by increase of S. aureus uptake, phagosome acidification and further stimulation of phago-lysosomes formation. Simultaneously, we tested influence of alantolactone on cytokines/chemokines production and p65 NF-κB concentration. The activity of alantolactone was compared with clarithromycin at concentration 20 µM.

Methods

The cytotoxicity of alantolactone as well as S. aureus uptake, pH of phagosomes and phago-lysosomes fusion were analysed with flow cytometry. Reactive oxygen species and superoxide production were evaluated spectrophotometrically. The efficiency of phagocytosis was evaluated via quantifying viable bacteria (CFU). The effect on p65 protein concentration and cytokine production by macrophages were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Alantolactone enhanced phagocytosis via increase of S. aureus uptake, acidification of phagosomes, and later stimulation of phago-lysosomes fusion. Alantolactone treatment resulted in ROS and superoxide production decrease. Furthermore, alantolactone inhibited production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8 as well as decreased p65 concentration, the subunit responsible for NF-κB activation and cytokine production and simultaneously stimulated release of anti-inflammatory mediators (IL-10 and TGF-β).

Conclusion

Results of our study indicate that alantolactone enhances clearance of S. aureus, and simultaneously modulates immune response, preventing collateral damage of the surrounding tissues. Considering the importance of phagocytosis in the pathogen killing, alantolactone may have a great potential as the supportive treatment of S. aureus infections. Further in vivo studies are warranted to confirm this hypothesis.

Antimicrobial peptides as therapeutic agents: opportunities and challenges

The rapid development of microbial resistance to conventional antibiotics has accelerated efforts to find anti-infectives with a novel mode-of-action, which are less prone to bacterial resistance. Intense nonclinical and clinical research is today ongoing to evaluate antimicrobial peptides (AMPs) as potential next-generation antibiotics. Currently, multiple AMPs are assessed in late-stage clinical trials, not only as novel anti-infective drugs, but also as innovative product candidates for immunomodulation, promotion of wound healing, and prevention of post-operative scars. The efforts to translate AMP-based research findings into pharmaceutical product candidates are expected to accelerate in coming years due to technological advancements in multiple areas, including an improved understanding of the mechanism-of-action of AMPs, smart formulation strategies, and advanced chemical synthesis protocols. At the same time, it is recognized that cytotoxicity, low metabolic stability due to sensitivity to proteolytic degradation, and limited oral bioavailability are some of the key weaknesses of AMPs. Furthermore, the pricing and reimbursement environment for new antimicrobial products remains as a major barrier to the commercialization of AMPs.

Fast and Slow-Growing Management Systems: Characterisation of Broiler Caecal Microbiota Development throughout the Growing Period

Simple Summary

This study was conducted to characterise the caecal microbiota in two broiler management systems (fast and slow-growing) during the growing period, using 16S rRNA sequencing analysis. Because of the essential role of the caecal bacteria in poultry health and productivity, these data could be considered as a biomarker of health status and will make it possible to evaluate different treatments applied in animals. The main results demonstrated that microbiota is in constant development throughout the growing period for both management systems, and the most abundant bacteria groups are related to better productive performance and intestinal health.

Abstract

Caecal microbiota and its modulation play an important role in poultry health, productivity and disease control. Moreover, due to the emergence of antimicrobial-resistant bacteria, society is pressing for a reduction in antibiotic administration by finding effective alternatives at farm level, such as less intensified production systems. Hence, the aim of this study was to characterise the caecal microbiota in two different broiler management systems, fast and slow-growing, using 16S rRNA sequencing analysis. To this end 576 broilers were reared in two different management systems (fast and slow-growing). Results showed that Firmicutes represented the dominant phylum for both systems. At the onset, Proteobacteria was the second prevalent phylum for fast and slow-growing breeds, outnumbering the Bacteroidetes. However, during the rest of the production cycle, Bacteroidetes was more abundant than Proteobacteria in both groups. Finally, regardless of the management system, the most predominant genera identified were Oscillospira spp., Ruminococcus spp., Coprococcus spp., Lactobacillus spp. and Bacteroides spp. In conclusion, fast and slow-growing broiler microbiota are in constant development throughout rearing, being relatively stable at 21 days of age. Regarding the genus, it should be noted that the three most abundant groups for both systems, Ruminococcus spp., Lactobacillus spp. and Bacteroides spp., are related to better productive performance and intestinal health.

Blueprint of epitope-based multivalent and multipathogenic vaccines: targeted against the dengue and zika viruses

Both dengue virus (DENV) and zika virus (ZIKV) belong to the highly infectious Flaviviridae family that has already caused several outbreaks and epidemics in many countries. DENV and ZIKV cause two of the most wide spread mosquito-borne viral diseases in the world, dengue fever (DENF) and zika fever (ZIKF), respectively. In many regions around the world, both of these diseases can outbreak together and can be lethal as well as life-threatening. Unfortunately, there is no functional and satisfactory vaccine available to combat these viruses. Therefore, in this study, we have attempted to design a blue print of potential multivalent and multipathogenic vaccines using immunoinformatics approach, which can combat both the DENV and ZIKV infections, simultaneously. Initially, three vaccines were designed; containing highly antigenic, non-allergenic, and non-toxic epitopes of T-cell (100% conserved) and B-cell from all the four DENV serotypes and ZIKV. In total, nine cytotoxic T-lymphocytic (CTL), nine helper T-lymphocytic (HTL), and seven B-cell lymphocytic (BCL) epitopes were used to construct three vaccines using three different adjuvants, designated as 'V1', 'V2', and 'V3'. Later, V3 was found to be the best vaccine construct, determined by molecular docking analysis. Thereafter, several in silico validation studies including molecular dynamics simulation and immune simulation were performed which indicated that V3 might be quite stable and should generate substantial immune response in the biological environment. However, further in vivo and in vitro validation might be required to finally confirm the safety and efficacy of our suggested vaccine constructs.Communicated by Ramaswamy H. Sarma.

Inhibition of Host Arginase Activity Against Staphylococcal Bloodstream Infection by Different Metabolites

Staphylococcus aureus is a notorious bacterial pathogen that often causes soft tissue and bloodstream infections and invariably garners resistance mechanisms against new antibiotics. Modulation of the host immune response by metabolites is a powerful tool against bacterial infections, but has not yet been used against S. aureus infections. In this study, we identified four metabolite biomarkers: L-proline, L-isoleucine, L-leucine, and L-valine (PILV), through a metabolomics study using animal models of S. aureus bloodstream infection. The exogenous administration of each metabolite or of PILV showed anti-infective effects, and a higher protection was achieved with PILV in comparison to individual metabolites. During the staphylococcal infection, the expression of most host arginase and nitric oxide synthase (NOS) isozymes was simultaneously induced in mouse liver, kidney, and blood samples. However, the induction of arginase isozymes was dramatically stronger than that of NOS isozymes. This elevated arginase activity was inhibited by the metabolite biomarkers thus killing S. aureus, and PILV exhibited the strongest inhibition of arginase activity and bacterial inhibition. The suppression of arginase activity also contributed to the metabolite-mediated phagocytic killing of S. aureus in mouse and human blood. Our findings demonstrate the metabolite-mediated arginase inhibition as a therapeutic intervention for S. aureus infection.

Within-host spatiotemporal dynamic of systemic salmonellosis: Ways to track infection, reaction to vaccination and antimicrobial treatment

During the last two decades our understanding of the complex in vivo host-pathogen interactions has increased due to technical improvements and new research tools. The rapid advancement of molecular biology, flow cytometry and microscopy techniques, combined with mathematical modelling, have empowered in-depth studies of systemic bacterial infections across scales from single molecules, to cells, to organs and systems to reach the whole organism level. By tracking subpopulations of bacteria in vivo using molecular or fluorescent tags, it has been possible to reconstruct the spread of infection within and between organs, allowing unprecedented quantification of the effects of antimicrobial treatment and vaccination. This review illustrates recent advances in the study of heterogeneous traits of the infection process and illustrate approaches to investigate the reciprocal interactions between antimicrobial treatments, bacterial growth/death as well as inter- and intra-organ spread. We also discuss how vaccines impact the in vivo behaviour of bacteria and how these findings can guide vaccine design and rational antimicrobial treatment.

Synthesis, characterization, antimicrobial and cytotoxic activity of novel half-sandwich Ru(II) arene complexes with benzoylthiourea derivatives

Three new ruthenium(II)-arene complexes, [Ru(η⁶-p-cymene)(L¹)Cl₂] (C1) where L¹ is N-((4 methoxyphenyl)carbamothioyl)benzamide; [Ru(η⁶-p-cymene)(L²)Cl₂] (C2) where L² is 4-(3-benzoylthioureido)benzoic acid and [Ru(η⁶-p-cymene)(L³)Cl₂] (C3) where L³ is methyl 4-(3- benzoylthioureido)benzoate have been synthetized, characterized and evaluated for their antimicrobial and anticancer activity. Characterization was performed using ¹H and ¹³C NMR, IR spectroscopy, mass spectrometry, electrical conductivity measurements and X-Ray diffraction analysis. X-Ray diffraction analysis of C1 showed typical expected "piano-stool" geometry with ruthenium coordinated to ligand via nitrogen and sulfur atoms of benzoylthiourea derivatives. Interesting, in herein described complex, upon coordination the four-membered ring was formed, instead of six-membered chelate common for this type of ligands. Cytotoxic activity was determined in human cervix adenocarcinoma (HeLa) cell line and IC₅₀ values ranged from 29.68 to 52.36 μM and the complexes were more active than related ligands (except in case of C2 where it is found that IC₅₀ value is close to IC₅₀ value of related ligand). Complex [Ru(η⁶-p-cymene)(L¹)Cl₂] (C1) expressed the highest cytotoxic activity with IC₅₀ value of 29.7 μM. Complexes and ligands were tested against nine Gram-positive and Gram-negative bacteria and one yeast- Candida albicans. Clinical Candida spp. strains from microbiological laboratories were included in testing processes as well. Minimum inhibitory concentrations values ranged from 62.5 μg/ml for complexes against Candida albicans to over 1000 μg/ml for several bacterial species.

Non-specific protection from respiratory tract infections in cattle generated by intranasal administration of an innate immune stimulant

Alternatives to antibiotics for prevention of respiratory tract infections in cattle are urgently needed given the increasing public and regulatory pressure to reduce overall antibiotic usage. Activation of local innate immune defenses in the upper respiratory tract is one strategy to induce non-specific protection against infection with the diverse array of viral and bacterial pathogens associated with bovine respiratory disease complex (BRDC), while avoiding the use of antibiotics. Our prior studies in rodent models demonstrated that intranasal administration of liposome-TLR complexes (LTC) as a non-specific immune stimulant generated high levels of protection against lethal bacterial and viral pathogens. Therefore, we conducted studies to assess LTC induction of local immune responses and protective immunity to BRDC in cattle. In vitro, LTC were shown to activate peripheral blood mononuclear cells in cattle, which was associated with secretion of INFγ and IL-6. Macrophage activation with LTC triggered intracellular killing of Mannheimia hemolytica and several other bacterial pathogens. In studies in cattle, intranasal administration of LTC demonstrated dose-dependent activation of local innate immune responses in the nasopharynx, including recruitment of monocytes and prolonged upregulation (at least 2 weeks) of innate immune cytokine gene expression by nasopharyngeal mucosal cells. In a BRDC challenge study, intranasal administration of LTC prior to pathogen exposure resulted in significant reduction in both clinical signs of infection and disease-associated euthanasia rates. These findings indicate that intranasal administration of a non-specific innate immune stimulant can be an effective method of rapidly generating generalized protection from mixed viral and bacterial respiratory tract infections in cattle.

Antimicrobial Resistance in ESKAPE Pathogens

Antimicrobial-resistant ESKAPE ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. The acquisition of antimicrobial resistance genes by ESKAPE pathogens has reduced the treatment options for serious infections, increased the burden of disease, and increased death rates due to treatment failure and requires a coordinated global response for antimicrobial resistance surveillance. This looming health threat has restimulated interest in the development of new antimicrobial therapies, has demanded the need for better patient care, and has facilitated heightened governance over stewardship practices.

Antimicrobial Resistance in ESKAPE Pathogens

Antimicrobial-resistant ESKAPE ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. The acquisition of antimicrobial resistance genes by ESKAPE pathogens has reduced the treatment options for serious infections, increased the burden of disease, and increased death rates due to treatment failure and requires a coordinated global response for antimicrobial resistance surveillance. This looming health threat has restimulated interest in the development of new antimicrobial therapies, has demanded the need for better patient care, and has facilitated heightened governance over stewardship practices.

Bacterial Lysates as Immunotherapies for Respiratory Infections: Methods of Preparation

Bacterial lysates, prepared from the microorganisms most frequently involved in human Respiratory Tract Infections (RTIs) have been in the market for several decades, and at present, several different brands are available in many countries worldwide. They all claimed to exert local and systemic immunomodulatory effects but different clinical trials show disparate results between them. The lack of consistency of predicted therapeutic effects has undermined their clinical use and hampered licensing in several countries. One explanation for such lack of consistency in the results is that their methods of preparation are also very different. Here, we review the available literature describing methods of preparation of bacterial lysates, including patent disclosure documents. We found a great variety of methodologies of preparation and a lack of standardized procedures among them. The main conclusion of our study is that there is a clear need for standardized protocols of production to obtain comparable results in clinical trials worldwide.

Balancing selection in Pattern Recognition Receptor signalling pathways is associated with gene function and pleiotropy in a wild rodent

Pathogen-mediated balancing selection is commonly considered to play an important role in the maintenance of genetic diversity, in particular in immune genes. However, the factors that may influence which immune genes are the targets of such selection are largely unknown. To address this, here we focus on Pattern Recognition Receptor (PRR) signalling pathways, which play a key role in innate immunity. We used whole-genome resequencing data from a population of bank voles (Myodes glareolus) to test for associations between balancing selection, pleiotropy and gene function in a set of 123 PRR signalling pathway genes. To investigate the effect of gene function, we compared genes encoding (a) receptors for microbial ligands versus downstream signalling proteins, and (b) receptors recognizing components of microbial cell walls, flagella and capsids versus receptors recognizing features of microbial nucleic acids. Analyses based on the nucleotide diversity of full coding sequences showed that balancing selection primarily targeted receptor genes with a low degree of pleiotropy. Moreover, genes encoding receptors recognizing components of microbial cell walls etc. were more important targets of balancing selection than receptors recognizing nucleic acids. Tests for localized signatures of balancing selection in coding and noncoding sequences showed that such signatures were mostly located in introns, and more evenly distributed among different functional categories of PRR pathway genes. The finding that signatures of balancing selection in full coding sequences primarily occur in receptor genes, in particular those encoding receptors for components of microbial cell walls etc., is consistent with the idea that coevolution between hosts and pathogens is an important cause of balancing selection on immune genes.

Exploiting the reverse vaccinology approach to design novel subunit vaccines against Ebola virus

Ebola virus is a highly pathogenic RNA virus that causes the Ebola haemorrhagic fever in human. This virus is considered as one of the dangerous viruses in the world with very high mortality rate. To date, no epitope-based subunit vaccine has yet been discovered to fight against Ebola although the outbreaks of this deadly virus took many lives in the past. In this study, approaches of reverse vaccinology were utilized in combination with different tools of immunoinformatics to design subunit vaccines against Ebola virus strain Mayinga-76. Three potential antigenic proteins of this virus i.e., matrix protein VP40, envelope glycoprotein and nucleoprotein were selected to construct the subunit vaccine. The MHC class-I, MHC class-II and B-cell epitopes were determined initially and after some robust analysis i.e., antigenicity, allergenicity, toxicity, conservancy and molecular docking study, EV-1, EV-2 and EV-3 were constructed as three potential vaccine constructs. These vaccine constructs are also expected to be effective on few other strains of Ebola virus since the highly conserved epitopes were used for vaccine construction. Thereafter, molecular docking study was conducted on these vaccines and EV-1 emerged as the best vaccine construct. Afterward, molecular dynamics simulation study revealed the good performances and stability of the intended vaccine protein. Finally, codon adaptation and in silico cloning were carried out to design a possible plasmid (pET-19b plasmid vector was used) for large scale production of the EV-1 vaccine. However, further in vitro and in vivo studies might be required on the predicted vaccines for final validation.

Functional Insights From the Evolutionary Diversification of Big Defensins

Big defensins are antimicrobial polypeptides believed to be the ancestors of β-defensins, the most evolutionary conserved family of host defense peptides (HDPs) in vertebrates. Nevertheless, big defensins underwent several independent gene loss events during animal evolution, being only retained in a limited number of phylogenetically distant invertebrates. Here, we explore the evolutionary history of this fascinating HDP family and investigate its patchy distribution in extant metazoans. We highlight the presence of big defensins in various classes of lophotrochozoans, as well as in a few arthropods and basal chordates (amphioxus), mostly adapted to life in marine environments. Bivalve mollusks often display an expanded repertoire of big defensin sequences, which appear to be the product of independent lineage-specific gene tandem duplications, followed by a rapid molecular diversification of newly acquired gene copies. This ongoing evolutionary process could underpin the simultaneous presence of canonical big defensins and non-canonical (β-defensin-like) sequences in some species. The big defensin genes of mussels and oysters, two species target of in-depth studies, are subjected to gene presence/absence variation (PAV), i.e., they can be present or absent in the genomes of different individuals. Moreover, big defensins follow different patterns of gene expression within a given species and respond differently to microbial challenges, suggesting functional divergence. Consistently, current structural data show that big defensin sequence diversity affects the 3D structure and biophysical properties of these polypeptides. We discuss here the role of the N-terminal hydrophobic domain, lost during evolution toward β-defensins, in the big defensin stability to high salt concentrations and its mechanism of action. Finally, we discuss the potential of big defensins as markers for animal health and for the nature-based design of novel therapeutics active at high salt concentrations.

From six to zero per cent Mycobacterium avium subsp. paratuberculosis milk ELISA positivity in three years - probably induced by Mycobacterium vaccae

This research communication reports the results of a study aimed at investigating the effects of introducing Mycobacterium vaccae on paratuberculosis carriage in a dairy herd. M. vaccae is a non-pathogenic member of the Mycobacteriaceae, with immunomodulatory and immunotherapeutic capabilities, acting by stimulating the cellular immune system, important in protection against paratuberculosis. Starting in 2014 we administered, by gavage, 1010 live M. vaccae bacteria to all new-born heifers on a dairy farm, first within 24 h of birth and again 2 weeks later. Paratuberculosis carriage was monitored yearly by milk ELISA. Faecal samples of 50% of cows, aged 3 years, born 1, 2 or 3 years before the experiment's onset, were tested by qPCR for MAP shedding and compared to 100% treated cows of the same age. Within 3 years, milk ELISA positivity was reduced from 6 to 0% and remained unchanged for the subsequent 2 years. One qPCR positive control cow was found each year for a total of 3 animals (2.46%). One positive cow (1%) was found among the treated cows. Two of the 3 positive control animals, still present on the farm at the end of 2019, tested negative whereas the positive test cow continued shedding MAP. M. vaccae shedding heifers mixing with adult cows were the probable means of the microorganism's propagation. The results of this investigation indicate that the introduction of live M. vaccae may be an inexpensive and fast alternative to current paratuberculosis control practices, justifying further exploration of the topic.

LC-MS/MS assay coupled with carboxylic acid magnetic bead affinity capture to quantitatively measure cationic host defense peptides (HDPs) in complex matrices with application to preclinical pharmacokinetic studies

Synthetic host defense peptides (HDP) are a new class of promising therapeutic agents with potential application in a variety of diseases. RP-182 is a 10mer synthetic HDP design, which selectively reduces M2-like tumor associated macrophages via engagement with the cell surface lectin receptor MRC1/CD206 and is currently being developed as an innate immune defense regulator to improve anti-tumor immunity in immunologically cold tumors. Herein, we describe a sensitive and specific liquid chromatography (LC) coupled to quadrupole electron spray tandem mass spectrometry method to measure positively charged HDPs and HDP peptide fragments in complex biological matrices. Carboxylic acid magnetic beads were used as an affinity-capturing agent to extract the positively charged RP-182 from both mouse plasma and tissue homogenates. Beads were eluted with 0.1% (v/v) formic acid and chromatographic separation was achieved on a Waters 2.1 × 100 mm, 3.5 μm XSelect Peptide CSH C18 column with a Vanguard pre-column of the same phase. MS/MS was performed on a Thermo TSQ Quantiva triple quadrupole mass spectrometer operating in Selected Reaction Monitoring (SRM) mode fragmenting the plus three parent ion 458.9⁺³ and monitoring ions 624.0⁺², 550.5⁺², and 597.3⁺¹ for RP-182 and 462.4⁺³ > 629.1⁺², 555.5⁺², and 607.3⁺¹ for isotopic RP-182 standard. The assay had good linearity ranging from 1 ng to 1000 ng in mouse plasma with the lower limit of detection for RP-182 at 1 ng in mouse plasma with good intra- and inter-sample precision and accuracy. Recovery ranged from 66% to 77% with minimum matrix effects. The method was successfully applied to an abbreviated pharmacokinetic study in mice after single IP injection of RP-182. The method was successfully tested on a second HDP, the 17mer D4E1, and the cationic human peptide hormone ghrelin suggesting that it might be a general sensitive method applicable to quantifying HDP peptides that are difficult to extract.

L-lysine potentiates aminoglycosides against Acinetobacter baumannii via regulation of proton motive force and antibiotics uptake

Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is a leading cause of hospital- and community-acquired infections. Acinetobacter baumannii can rapidly acquire diverse resistance mechanisms and undergo genetic modifications that confer resistance and persistence to all currently used clinical antibiotics. In this study, we found exogenous L-lysine sensitizes Acinetobacter baumannii, other Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and a Gram-positive bacterium (Mycobacterium smegmatis) to aminoglycosides. Importantly, the combination of L-lysine with aminoglycosides killed clinically isolated multidrug-resistant Acinetobacter baumannii and persister cells. The exogenous L-lysine can increase proton motive force via transmembrane chemical gradient, resulting in aminoglycoside acumination that further accounts for reactive oxygen species production. The combination of L-lysine and antibiotics highlights a promising strategy against bacterial infection.

Broad-spectrum suppression of bacterial pneumonia by aminoglycoside-propagated Acinetobacter baumannii

Antimicrobial resistance is increasing in pathogenic bacteria. Yet, the effect of antibiotic exposure on resistant bacteria has been underexplored and may affect pathogenesis. Here we describe the discovery that propagation of the human pathogen Acinetobacter baumannii in an aminoglycoside antibiotic results in alterations to the bacterium that interact with lung innate immunity resulting in enhanced bacterial clearance. Co-inoculation of mice with A. baumannii grown in the presence and absence of the aminoglycoside, kanamycin, induces enhanced clearance of a non-kanamycin-propagated strain. This finding can be replicated when kanamycin-propagated A. baumannii is killed prior to co-inoculation of mice, indicating the enhanced bacterial clearance results from interactions with innate host defenses in the lung. Infection with kanamycin-propagated A. baumannii alters the kinetics of phagocyte recruitment to the lung and reduces pro- and anti-inflammatory cytokine and chemokine production in the lung and blood. This culminates in reduced histopathologic evidence of lung injury during infection despite enhanced bacterial clearance. Further, the antibacterial response induced by killed aminoglycoside-propagated A. baumannii enhances the clearance of multiple clinically relevant Gram-negative pathogens from the lungs of infected mice. Together, these findings exemplify cooperation between antibiotics and the host immune system that affords protection against multiple antibiotic-resistant bacterial pathogens. Further, these findings highlight the potential for the development of a broad-spectrum therapeutic that exploits a similar mechanism to that described here and acts as an innate immunity modulator.

Preserving the ability to treat infectious diseases with antibiotics in the face of the rapid proliferation of drug-resistant bacterial pathogens is among the greatest challenges facing medicine. Efforts to combat antimicrobial resistance may include strategies to maximize the utility of existing antibiotics while also identifying new therapeutic targets to treat bacterial infections. Acinetobacter baumannii is a human pathogen and strains of A. baumannii have acquired multi- and pan-antibiotic resistance. Here, we demonstrate that A. baumannii that is resistant to the aminoglycoside class of antibiotics is rapidly cleared from the lungs of mice when exposed to aminoglycoside antibiotics. Exposure to aminoglycosides induces changes in A. baumannii that interact with mouse antibacterial defenses, leading to rapid clearance of the infection. Further, killed aminoglycoside-exposed A. baumannii interacts with innate immunity in the lung to enhance the clearance of other pathogenic bacteria. These findings indicate that pneumonia caused by aminoglycoside-resistant A. baumannii may be effectively treated with aminoglycoside antibiotics and also suggests that the host immune response can be targeted to enhance the clearance of bacterial infections.

Quantification of immuno-regulatory cytokine and toll-like receptors gene expression in dogs with generalized demodicosis

The proliferation of Demodex mites is mainly controlled by host immunity; however, the precised mechanism of host-mite interplay and host immune response in the cutaneous microenvironment of dogs with generalized demodicosis (GD) are not yet established. In the present study, we envisaged the alterations in the expression of toll-like receptors (TLRs) and immuno-regulatory cytokine gene in the skin lesions and peripheral blood mononuclear cells (PBMCs) of dogs with GD. The expression of TLR2, TLR6, IFN-γ, TGF-β and IL-10 genes in the skin lesions and PBMCs of 15 dogs with GD was quantified by qRT-PCR. Compared to healthy dogs, significantly elevated expression of TLR2 (P = 0.048), TGF-β (P = 0.04) and IL-10 (P = 0.012) were found in the PBMCs of dogs with GD. Conversely, there was significantly reduced expression of TLR6 gene (P = 0.021) in the PBMCs of these dogs. The infested dogs also revealed significantly elevated expression of TLR2 gene (P = 0.034) in the skin lesions, while, the expression of the TLR6 gene was found to be significantly (P = 0.004) reduced. Interestingly, significant alterations in TGF-β (P = 0.105) and IL-10 (P = 0.162) genes expression were not observed in the skin lesions of diseased dogs. Our findings suggest that Demodex mites contribute to a different systemic and cutaneous immune response in dogs for their proliferation, and consequently the development of GD. Therefore, Demodex mites might be inducing the immunosuppression through activating the systemic over-expression of immunosuppressive cytokines; however, in the cutaneous lesions, the expression of immunosuppressive cytokines remained unaltered. Both systemic and local over-expression of TLR2 and reduced expression of TLR6 genes might be responsible for the inflammatory signs of canine demodicosis and helping to the mite to escape the host immunity.

Ruthenium Bipyridyl Dithiocyanate Complex Exerted Adjuvant Activity on the Activated Mammalian Macrophages in vitro

A cell's function can be regulated through its mechanism, and there has been a growing body of literature on how immune cells' metabolism shapes its overall immune response. Manipulation of the cells metabolic activity through a biocompatible material would present new venues to the field of medicine. These agents are known as immunomodulatory and immunostimulatory reagents. They can either stimulate the immune response in a disease case where the immune response is lacking the strength or they can determine the nature and strength of the immune response as an immunomodulator according to our needs to cope with certain disorders. In our recent studies, we have been examining different kinds of materials on the macrophages in order to delineate their immunostimulatory or immunomodulatory potentials. Ruthenium-based materials have gathered our attention due to their ability to get involved into the electron mobility processes in the solar cells. In line with our expectations, probably by interfering the electron transport processes of the macrophages, ruthenium bipyridyl dithiocyanate complex had a stark immunomodulatory function on the LPS-activated mammalian macrophages in vitro. Our results support that it can be utilized as an adjuvant in the new generation vaccines.

Future Antibacterial Strategies: From Basic Concepts to Clinical Challenges

This review presents potential benefits and limitations of innovative strategies that are currently investigated for the discovery of novel antibacterial agents to prevent or treat infections caused by multidrug-resistant organisms.